Pipette device

ABSTRACT

A pipetting arrangement comprising a carrier ( 10 ) to which first ends of a plurality of mutually parallel nozzles ( 20 ) are connected with the aid of respective screw joints ( 21, 22 ), wherein the nozzles are spaced only a slight distance apart, wherein second ends ( 24 ) of said nozzles ( 20 ) are designed to carry a readily replaced pipetting tip ( 30 ), and wherein the pipetting arrangement also includes means ( 7, 8, 17, 18, 12 ) for establishing at said second end of a respective nozzle ( 20 ) a selective pressure for sucking fluid into and dispensing fluid from said tips. The nozzles are provided at their respective second ends ( 24 ) with a driving formation ( 28, 28 ′) to which there can be applied a turning tool for respectively tightening and loosening the screw joint ( 21, 22 ).

The present invention relates to a pipetting arrangement of the kinddefined in the preamble of claim 1.

A pipetting arrangement of this kind is known from GP 1136127 A. Thepipetting arrangement includes a carrier to which first ends ofrespective nozzles in a plurality of mutually parallel nozzles areconnected with the aid of a respective screw joint, wherein the nozzlesare spaced only a slight distance apart, and wherein second ends of saidnozzles are designed to carry a readily replaced pipetting tip. Thepipetting arrangement also includes means for establishing at saidsecond end a selectable pressure for sucking fluid into and dispensingfluid from said tips. The carrier can be rotated to enable the tips tobe inserted into respective fluid volumes for the suction of fluidtherefrom.

One problem with this type of pipetting arrangement is that the nozzlesmust be situated tightly adjacent one another, for space reasons. Toenable the establishment of respective releasable screw joints to beachieved, each nozzle has around its periphery in the proximity of thescrew joint an hexagonal fitting which enables the nozzle to be rotatedwith the aid of an hexagonal wrench or some corresponding tool. A nozzlethat malfunctions must be replaced. However, because the nozzles lie soclose together it is not normally possible to grip a nozzle that issituated inwardly of a nozzle row. Consequently, it will be necessaryfor an operator to remove a number of nozzles in turn, starting from theend of at least the row in which the malfunctioning nozzle is situated.It may be necessary to remove nozzles from several rows, starting fromtheir respective ends, before the malfunctioning nozzle can be reachedand replaced. After the malfunctioning nozzle has been replaced, thenozzles that were dismantled must be replaced. The problem becomesparticularly troublesome when the nozzles are disposed very closetogether in a matrix that includes several parallel rows of nozzles.However, the problem is also troublesome in the case of apparatus thatinclude only a single row of nozzles.

The object of the present invention is to provide a pipettingarrangement with which a single malfunctioning nozzle can be readilyreplaced without requiring closely situated functioning nozzles to bedismantled and re-fitted as a result thereof.

This object is achieved by means of the present invention.

The invention is defined in the accompanying claim 1.

Other embodiments of the present invention will be apparent from theaccompanying dependent claims.

Basically, the present invention involves providing the second ends ofthe nozzles with a respective driving formation to which a nozzleturning tool can be applied axially without being obstructed by nearbynozzles. The tool can then be rotated to loosen or tighten the screwjoint of the nozzle concerned.

The driving formation on the second end is preferably centred coaxiallyon the nozzle. The driving formation may consist in an end-groove in anaxial plane to the nozzle, so as to enable the nozzle to be driven by aflat-headed screwdriver. Alternatively, the driving formation mayconsist in a crosscut groove which is centred in relation to the nozzleaxis and which can be driven by a cross-mouthed driver. Analogousdriving formations and driving tools will be obvious to the person ofaverage skill in this art.

Since the nozzle narrows conically from its second end down towards theextremity of said end with a total front rake angle of five (5) degrees,for instance, over a length of seven (7) mm for instance, the risk ofthe driving tool interfering with nearby nozzles when fitting ordismantling nozzles is minimised. The conicity of a nozzle enables acorresponding conical end-part of a nozzle tip of the pipettingarrangement to be readily fastened.

The invention will now be described by way of example with reference tothe accompanying drawings, in which

FIG. 1 is a schematic partially sectioned view of a pipettingarrangement;

FIG. 2 is a perspective reproduction of a tubular nozzle for anarrangement constructed in accordance with the present invention;

FIG. 3 illustrates schematically a tool for rotating the nozzle shown inFIG. 2; and

FIG. 4 is an end view of another embodiment of the nozzle.

FIG. 1 shows a carrier 10 which is provided with a row of mutuallyparallel through-penetrating bores 11 that have on the under side of thecarrier a widened section which includes an internal screw thread 21. Atubular nozzle 20 has on its first end an external screw thread 22 whichco-acts with the internal thread 21. The nozzle 20 has a centralpassageway 12 which corresponds to the passageway or through-penetratingbore 11. A piston rod 17 carries a piston 18 which is received in thepassageway 12 and can be drawn out through the passageway 11. The lowersecond end 24 of the nozzle narrows conically for receiving a pipettingtip 30, which must be frequently replaced.

The piston rod may have the same diameter as the piston. This enablesthe carrier 10 to be formed by two mutually affixed plates that havemutually aligned openings corresponding to the bores/passageways 11,wherein the plates have contact surfaces that lie generally in a planenormal to the axes of said passageways, and wherein at least one of thecontact surfaces includes a recess for accommodating a sealing ring (anO-ring) that seals against the piston rod/piston.

The piston rods 17 are carried by a displaceable bar 7 which can bemoved relative to the carrier 10 and parallel therewith, such as to drawa volume of fluid into the tips 30 when the piston is withdrawn and todispense a volume of fluid when the piston 18 is driven down.

In an embodiment at present preferred (FIG. 2), the conical section 24of the nozzle 20 includes two axially spaced annular conical parts 24′,24″, these annular parts being separated by a peripheral groove 29 foraccommodating a sealing ring 25, e.g. an O-ring, which provides a sealaround a tip 30, e.g. a plastic tip. The free end part of the nozzle 20is purely cylindrical. The recess is replaced with a screw driver slot 8in the axial plane of the nozzle at its free end.

A driver 40 (FIG. 3) has a blade 128 which fits into the slot 28. Asshown, the blade may carry a pin 112 that is received in the passageway12. As shown in FIG. 3, the driver 40 may include a handle 42 connectedto the blade 128 by means of a shank 41.

When a tip 30 is removed from the conical part of a nozzle, the blade128 of the driver 40 can be inserted into the groove coaxially with thenozzle 20, so as to loosen or establish respectively the screw joint 21,22.

FIG. 4 illustrates schematically an alternative to the groove 28, in theform of a cruciform groove 28′ which is centred in relation to the axisof the nozzle 20 and which accommodates the blade of a cross-headeddriver.

The carrier 10 is displaceable relative to a microtitration plate, sothat the tips 30 can be respectively inserted into and raised from thebasins in said plate. The means for moving the carrier (the nozzles 20)in relation to the microtitration plates form no part of the inventionand will not therefore be described in detail.

It will also be understood that devices other than the pistons 18 andtheir drive means may be provided to establish a subpressure and anoverpressure in the passageway 12 at the free end of the nozzle. Forinstance, a central overpressure and subpressure source may be connectedrespectively to the free ends of the nozzles 20 for sucking anddispensing fluid into and from the tips 30, 40.

The pipetting tips 30 are of a conventional design and suitably have theform of a conical rotational-symmetrical shell which at its larger endhas essentially the same conicity as the conical end part 24 of thenozzle 20.

The fact that the end part 24 narrows towards its tip enables thedriving formation to be established alternatively around the peripheryof said end part, since a tool co-acting therewith, for instance asocket wrench, may also in practice have an outer diameter which issmaller than the pitch between mutually adjacent nozzles, and may alsohave a diameter that is smaller than the outer diameter of said nozzleswhen adjacent nozzles are in radial contact with each other.

1. A pipetting arrangement that includes a carrier (10) to which firstends of a plurality of mutually parallel nozzles (20) are connected withthe aid of respective screw joints (21, 22), wherein the nozzles arespaced only a slight distance apart, wherein second ends (24) of saidnozzles (20) are designed to carry a readily replaced pipetting tip(30), and wherein the pipetting arrangement also includes means (7, 8,17, 18, 12) for establishing at said second end of a respective nozzle(20) a selective pressure for sucking fluid into and dispensing fluidfrom said times, characterised in that the nozzles are provided at theirrespective second ends (24) with a driving formation (28, 28′) to whichthere can be applied a turning tool for respectively tightening andloosening the screw joint (21, 22).
 2. An arrangement according to claim1, characterised in that the driving formation (28) includes a groove onthe free end of the nozzle in the axial plane thereof, wherein the toolincludes a blade that co-acts with the groove.
 3. An arrangementaccording to claim 1, characterised in that the driving formation (28′)is a cross-shaped groove which is centred with respect to the axis ofthe nozzle (20), wherein the tool includes a cross-headed blade forco-action with the cross-shaped groove (28′).
 4. An arrangementaccording to claims 1-3, characterised in that the nozzle (20) hasadjacent its second end a narrowing end portion (24) to which a tip (30)can be tightly and removable attached.
 5. An arrangement according toclaim 4, characterised in that the end portion (24) of the nozzle has aperipheral groove (29) which carries a sealing ring (25) which sealsagainst the inner circumference of the pipetting tip (30).